1. Field of the invention
The present invention relates generally to optical head devices for use in disc players, and more particularly, to an optical head device for generating and controlling a light beam incident upon an optical record disc loaded on a disc player and for detecting the light beam emerging from the optical record disc.
2. Description of the Prior Art
In an optical disc player for reproducing information recorded on an optical record disc, an optical head device is provided for constituting an optical arrangement to read information from a record track formed on the optical record disc loaded on the optical disc player. An example of such an optical head device proposed previously is arranged as schematically shown in FIG. 1.
This optical head device is formed into a unit containing a semiconductor laser element 11, a photodetector 20 and other optical parts and movable in the direction of the radius of a record disc D. In the unit, a laser light beam generated by the semiconductor laser element 11 is diffracted by a diffraction grating 12 to be divided into three beams, which are represented with a single solid line in FIG. 1 for the sake of simplification, and each of the three laser light beams is subjected to a change of direction of the axis thereof by a beam splitter 13 to enter into a collimator lens 14. The laser light beam collimated by the collimator lens 14 is caused to impinge upon the record disc D through an object lens 16 and reflected from the record disc D after being subjected to modulations at a record track formed on the record disc D.
The reflected laser light beam emerging from the record disc D returns through the object lens 16 and the collimator lens 14 to passing through the beam splitter 13 without a further change of direction of the axis thereof and then is guided through a light receiving lens 18 to the photodetector 20. Then, detection output signals obtained from the photodetector 20 are supplied to a signal processing circuit (not shown in FIG. 1) to produce, for example, a reproduced information signal, a focus control signal and a tracking control signal.
The focus and tracking control signals obtained from the signal processing circuit are supplied respectively to a focus control driver 21 and a tracking control driver 22 both provided in relation to the object lens 16. The focus control driver 21 is operative to move the object lens 16 in a direction along the optical axis thereof to approach or recede from the record disc D in response to the focus control signal supplied thereto, and the tracking control driver 22 is operative to move the object less 16 so as to shift the laser light beams incident upon the record disc D in a direction transverse to the record track in response to the tracking control signal supplied thereto.
The optical head device constituted as described above is provided with its overall shape and dimension, the size of each portion thereof and so on in accordance with the shape, size, function and so forth of a disc player to which the optical head device is applied. That is, generally, an optical head device is designed and produced to be dedicated to each type of disc player and therefore, for example, an optical head device for use in a disc player used on a table is different in shape, size and weight from an optical head device for use in a portable disc player. Therefore, for supplying optical head devices for use in various types of disc players, it is required to design and produce a plurality of different types of optical head devices each dedicated to each of the disc players. This results in that a relatively long term and a relatively large amount of expence are spent and various facilities are required for designing and producing the optical head devices, so that the production co t of the optical head device is increased.